This invention relates to a synthetic resin bag which can be easily opened by way of a tear string and which can stand alone in a stable state when put on a shelf in a shop or in home use.
There has thus far been known a synthetic resin bag B as shown in FIGS. 16 to 19, which can keep a stand-up position in a stable state when put on a shelf or a similar support surface in a shop or in home use.
As seen in these figures, the synthetic resin bag B includes a couple of overlapped front and rear walls 50 and 51 and a bottom wall 52 folded in an inverted V-shape and inserted between the lower ends of the front and rear walls 50 and 51. The front and rear walls 50 and 51 are welded to each other by heat sealing in marginal edge portions at each side except the lower side where the marginal edge portions of the front and rear walls 50 and 51 are heat sealed to lower marginal edge portions of the bottom walls 52 to form a bag body 53.
Further, as shown in FIGS. 16 to 19, the bag B is provided with a transverse sealing fastener 54 in a top portion of the bag 53 across the width thereof.
As seen in FIG. 17, the sealing fastener 54 is composed of an elongated female member of U-shape in cross-section which is thermally welded on the inner side of the front wall 50, and an elongated coupling protuberance 56 which is formed on the inner side of the rear wall 51 and which is disengageably engageable with a coupling groove on the part of the female member 55.
The synthetic resin bag B with such an arrangement is folded in a flat shape when in an empty state free of any filling material, as seen in the longitudinal section of FIG. 17.
On the other hand, when the upper end of the synthetic resin bag B is cut off and the sealing fastener 54 is uncoupled to fill a material into a packing space 56 in the bag 53, the bottom wall 52 of inverted V-shape is unfolded and stretched toward the front and rear sides to form a flat bottom as shown in FIG. 19. As a result, a packing space with an ample breadth is formed in the bag 53 so that a large quantity of material can be packed in the bag 53.
Besides, the synthetic resin bag B of the above arrangement has a flat bottom surface of a sufficient breadth when in filled state, as shown in FIG. 19, so that one can put it in a stand-up position on a shelf or on a similar support surface for storage or display or for other purposes.
However, the conventional synthetic resin bag B with the above-described construction still has a number of problems to be solved as discussed below.
Namely, when in an unfilled empty state or in a flatly folded state with one side overlaying on the other as shown in FIG. 16, normally the synthetic resin bag B has a rectangular shape with one and same width W from the upper to lower end thereof in front view.
Therefore, when the bag 53 is packed with a certain quantity of filling material, the bottom wall 52 of inverted V-shape is unfolded and flatly spread toward the front and rear sides and, as shown in FIG. 19, the front and rear walls bulge out toward front and rear sides mainly in the respective center portions except their upper portions where the bag is not packed with the filling material. Consequently, in contrast to the unfilled upper portions which retain the original width W, the packed portions of the bag are deformed to have a narrower width w which is markedly smaller than the width W of the unfilled upper portions. This means that, when the bag is put on a shelf or a similar support surface, it would stand in an extremely unstable state as seen in FIG. 19.
Therefore, at the time of putting such synthetic resin bags B on or off a shelf or the like, it is very likely that the synthetic resin bags B easily fall down when upper portions of adjacent bags come into abutting contact with each other. Visually, such a look gives customers an impression of instability which might impair their buying aspirations.
Further, when placing the synthetic resin bags B side by side on a shelf, the adjacently located bags come into contact with each other firstly in their broader or wider upper portions, leaving wasteful spaces between the lateral sides of the adjacently located bags B and thus limiting the number of the synthetic resin bags B which can be placed on a shelf in terms of an area per unit length.
It is an object of the present invention to provide a synthetic resin bag which can solve the above-mentioned problems.
According to the present invention, there is provided an easily openable synthetic resin bag which is characterized by the provision of: a) a bag body proper having in an overlapped state front and rear walls of substantially rectangular shape, and a bottom wall interposed between the lower ends of the front and rear walls and having opposite side edges folded down in an inverted V-shape, the front and rear walls being thermally welded to each other along lateral and upper marginal edges to form lateral marginal seal portions and an upper marginal seal portion, the front and rear walls having marginal edge portions at the respective lower ends thermally welded to marginal edge portions at the opposite lower ends of the bottom wall to form lower marginal seal portions, and lower end portions of the front and rear walls being thermally welded to lower end portions of the bottom wall forming a pair of corner portions, said corner portions respectively having oblique sealing lines forming triangles between a lower end portion of each lateral marginal seal portion and opposite end portions of the lower marginal seal portions to form obliquely cut seal portions; and b) a tear string heat sealed on the inner side of the rear wall along an opening line at the upper end of the bag body and having opposite end portions thereof heat sealed in gripped state between corresponding portions of the lateral marginal seal portions of the bag body; the bag body having a width gradually broadened in a tapered fashion from the upper to lower end thereof.
In the foregoing bag construction, the present invention has further features as given below.
(1) The bag body is so shaped as to have at the upper end thereof an opening of a width larger than the width between lower ends of obliquely cut seal portions contiguously connected to the lower seal portions, but smaller than the width between the upper ends of the obliquely cut seal portions. PA1 (2) A portion of the left-hand lateral marginal seal portion of the bag body is bulged out to form an ear portion at a position corresponding to the tear string, the ear portion being provided with a pulling tab so arranged as to be peelable from the left-hand lateral marginal seal portion integrally together with one end of the tearing string.